This invention relates to electrostatic dissipative polycarbonate compositions including compositions suitable for injection molding applications.
Polycarbonate (PC) continues to be one of the leading engineering thermoplastics due to its balance of toughness, clarity, high heat deflection properties, dimensional stability, good electrical characteristics, and flame retardancy capabilities. PC is commonly used in injection molding applications.
Thermoplastic polyurethanes (TPU) are unique thermoplastic elastomers with excellent abrasion resistance, outstanding low-temperature performance, excellent mechanical properties, very good tear strength, high elasticity, high transparency, good oil and grease resistance.
Tremendous synergies would be achieved if the strengths of these two materials could be combined. However, due to the relatively high melt viscosity (i.e., low melt flow) of PC, these materials are usually molded at 280-300° C., which is about 50° C. higher than the safe processing temperatures of TPU. Thus, attempts to combine these materials lead to severe degradation of the resulting compositions when they are exposed to the processing temperatures required for the PC component. In addition, poor compatibility between PC and TPU often leads to delamination and poor surface quality in molded parts made from such compositions.
There is a need for compositions that combine the properties of PC and TPU while avoiding the problems of high temperature degradation and delamination and poor surface quality in molded parts resulting from poor compatibility of the components that often result from such combinations. The present invention deals with such compositions.
There is also a need for such compositions to have good electrostatic dissipative (ESD) properties. Currently, antistatic agents or conductive fillers (e.g., carbon black) must be added to many compositions in order to allow their use in various applications, such as packaging applications where good ESD properties are required. Replacing composition that must contain conductive fillers or antistatic agents with compositions that are inherently dissipative would result in safer permanent ESD protection and higher cleanliness. The present invention deals with such compositions.
There is also a need, in the production of ESD sensitive electronic devices, such as hard disk drives, for materials that have good ESD properties, good cleanliness properties (little to no fillers), good mechanical properties, and good thermal properties, which can be injection molded. The present invention deals with such compositions.